Rotatable boring tools frequently require fine radial adjustment of the cutting tool relative to the axis of rotation of the mounting head. This is equally necessary under circumstances where a rotatable cutting tool is used where a stationary cutter is employed with a rotating work piece. Adjustment is conventionally accomplished in various ways at or near the mounting of the cutting tool on the boring bar; for example, a cutting tool cartridge may be mounted on the boring bar with adjustable means such as disclosed in the U.S. Pats. Nos. 3,102,441, 3,236,125 and 4,428,704. In other cases the tool bit is mounted at the end of the boring bar adjustable through a slide provision such as shown in U.S. Pat. No. 3,703,755 or adjustably mounted per se as disclosed in U.S. Pat. No. 3,171,188.
In many cases, particularly in tools for boring small diameters in elongated holes, the adjustment mechanism, as in the case of cartridges, involves a mounting pocket of undue dimensions relative to the diameter of the boring bar so that some provision for pivoting or laterally moving the projecting boring bar relative to the rotatable mounting head is desirable. Some tool holders utilize an internal adjustment member involving radially extending internal arms which may result in unbalanced tools and problems such as chattering and poor repeatability. One type of known tool holder is disclosed in U.S. Pat. No. 3,753,624, wherein a tool shank is supported within a housing by a forward pivotal support and an elastic rearward support which may be overcome for adjustment, causing the central shaft member to tilt radially outward. In such tool when sufficient resilient force is applied to the cutting edge, the resilient force at the rear portion of the shank may be overcome resulting in chattering.